Conventionally, in the field of blood drawing, a blood component, platelets for most of cases, is collected from drawn blood and other blood components are returned into the blood donor. In such operation, a blood component separation device including a centrifugal separator is used.
In recent years, in the field of radiation therapy for cancer or the like, transfusion of platelet liquid is widely performed, and high-concentration platelet liquid is necessary for the therapy. To obtain high-concentration platelet liquid, Patent Literature 1 discloses an art using a blood component separation device to temporarily store low-concentration platelet liquid in a buffy coat bag and store only high-concentration platelet liquid in a platelet intermediate bag.
As for the blood component separation device disclosed in Patent Literature 1, blood is previously stored in at least one of two blood bags, and anticoagulant, such as ACD (acid-citrate-dextrose) liquid, is added to the previously stored blood to prevent coagulation.